In recent years, there has been a strong demand to lighten the weights of vehicles in order to reduce energy consumption, and in order to meet this demand, cast aluminum alloys such as A390 have been used in the compressor parts and oil pump covers of vehicles. These aluminum alloys have been widely used in engines and other wear-resistant parts for excelling in wear resistance.
A390 aluminum alloy has a composition containing 16.0-18.0 mass % of Si, 4.0-5.0 mass % of Cu, 0.45-0.65 mass % of Mg, less than 0.5 mass % of Fe, less than 0.1 mass % of Mn and less than 0.20 mass % of Ti, and is characterized by the addition of large amounts of Si in order to achieve the necessary wear resistance.
However, as the Si content increases, the liquidus temperature of the aluminum alloy rises, thus requiring the aluminum alloy to be melted and cast at a higher temperature than is generally used. As a result, not only must an expensive lining refractory material be used, but there are various other drawbacks such as reduced furnace durability, increased fuel consumption and reduced durability of the casting dice. Additionally, there are problems such as the distribution of primary crystal Si becoming uneven, and casting defects such as voids.
Additionally, hyper-eutectic Al-Si alloys excelling in wear resistance and burn resistance such as die-cast alloy JIS ADC14 are used in a manner similar to the above alloy. Furthermore, the applicant of the present application has also developed aluminum alloys such as those disclosed in JP-A H5-78770 and JP-A H7-252567 as wear-resistant alloys, and these have been patented as Japanese Patent No. 2709663 and Japanese Patent No.3378342.    Patent Document 1: JP-A H5-78770    Patent Document 2: JP-A H7-252567
The above patents are for a cast aluminum alloy excelling in wear resistance, characterized by comprising 14.0-16.0 wt % of Si, 2.0-5.0 wt % of Cu, 0.1-1.0 wt % of Mg, 0.3-0.8 wt % of Mn, 0.1-0.3 wt % of Cr, 0.05-0.20 wt % of Ti, 0.003-0.02 wt % of P, and 1.5 wt % or less of Fe, wherein the Ca content is limited to less than 0.005 wt % and having a uniform dispersion of primary crystal Si with an average grain size of 10-50 μm; and a cast aluminum alloy excelling in wear resistance, characterized by comprising 14.0-16.0 wt % of Si, 2.0-5.0 wt % of Cu, 0.1-1.0 wt % of Mg, 0.3-0.8 wt % of Mn, 0.1-0.3 wt % of Cr, 0.01-0.20 wt % of Ti, 0.003-0.02 wt % of P, and 1.5 wt % or less of Fe, wherein the Ca content is limited to 0.005 wt % or less, and primary crystal Si and Al—Si—Fe—Mn—Cr intermetallic compounds are both dispersed as crystals with a grain size of 5-30 μm.